It sounds just fine to me. I have tried other solutions for mid-bass without any particular success. It did have an array of eight 10" covering some ~100 to ~300 Hz. Actually, the big 21" H-frames were better to my ears.

Others do run woofers and especially midranges way above the dipole peak, and we are talking several octaves.... I would not do that because the off-axis response gets weird, but from the dipole peak and down the dipole figure-8 pattern is there, but not above.

Yes 100Hz is an experimental approximative number when you use 2x10" in the H Frame It is just a point of reference for discussion.

Jerome,
I use 2x10" drivers in a H frame up to 400 Hz - without complaints. And that is almost one octave below the dipole peak. I would be thankfull if you could give the slightest hint, what kind of physics forbids going beyond 100 Hz.

Rudolf : Stored energy... I made this project :Ultimate OB Gallery
And I heard something wrong in the mid, and I notice a lot of stored energy (see attachments).
Easy for me to conceive, a mass of air cannot do mid, but good for bass.